The Sultan of Brunei can be thought of as synonymous with the ruling House of Bolkiah, with descendency being traced from the 1st sultan, temporarily interrupted by the 14th sultan Abdul Hakkul Mubin who in turn was deposed by a member of the House of Bolkiah. It is not clear when the house became known as the 'House of Bolkiah', and whether it was named after the current sultan Hassanal Bolkiah, or the 6th sultan Bolkiah.
The full title of the Sultan is: His Majesty The Sultan and Yang Di-Pertuan of Brunei Darussalam.
The earliest historical record of the Sultans of Brunei is not clearly known due to the poor early documentation of Brunei history. In addition there has been an effort to Islamise the history, with the "official history" not matching up with verifiable foreign sources  The Batu Tarsilah - the genealogical record of the kings of Brunei - was not started until 1807. Therefore, much of the intepretation on history relied on earlier Chinese sources and legends. It seems that the early Sultanate of Brunei was dependent on Chinese support, and perhaps early Sultans were of Chinese origin. Furthermore the earliest Sultans may have been practising the Hindu or Buddhist religions, with early names indicating this origin.